Scientists create first all-carbon solar cell

Cost improvements, but low efficiency

Researchers at Stanford University have developed a solar cell made entirely of carbon, offering a cheaper alternative to the current standard.

Solar cells that typically use more expensive materials such as indium tin oxide (ITO) - also used in smartphones, LCD screens and many other applications - and are known as rare earth minerals.

Now, a team of researchers at Stanford University have come up with an alternative method of production by creating the first solar cell made entirely of the abundant resource, carbon.

The cell consists of a photovoltaic layer sandwiched between two electrodes. Typically these electrodes would be made of conductive metals like ITO, but the researchers used atom-thick material carbon-based material graphene and carbon nanotubes, essentially rolled nano-scale sheets of carbon.

According to the researchers, carbon nanotubes have significantly better electrical conductivity and light absorption properties and would allow for easier production than conventional cells.

However, the efficiency is not able to reach the levels of conventional cells - currently only able to reach conversion rates of one percent.

The team is confident that this can be improved, and is looking at ways to increase the efficiency by, for example, creating smoother layers of material to make it easier to collect current.

One of the problems is that the prototype device absorbs wavelengths of light in the near to the infrared spectrum. But if the researchers are able to find ways of making the carbon nanomaterials target wider wavelengths, and on the visible spectrum, this could improve efficiency.

Even if it is not possible to massively increase the efficiency of cells there should be some uses. Carbon, which forms super-strong diamonds, is a resilient material and can remain stable at high temperatures where other cells would stop working.

"We believe that all-carbon solar cells could be used in extreme environments, such as at high temperatures or at high physical stress," Michael Vosgueritchian, one of the researchers, said. "But obviously we want the highest efficiency possible and are working on ways to improve our device".